Deasphalting operation



United States PatentO 8' DEASPHALIING .OPERATION BarneyR.Strickland,y Westleld; N. Jv., assigner, tojStandard .OilDevelopment Company, l a corporation of Delaware The ,'Presentsinvention .is :broadly l.eencetned withv an improvedl process for the removalf asphaltic constituents from residual A. oils, whereby increasedyiells of higher quality deasnhaltedoils are obtained-- The Zpresent inventiQn Yis 'mQre-,partieularlv Concerned' A.with an improvedflprocess, for the prepa-ration.- ofsatisfa ctory feed Stocks .for fsreekins. secretions; .whereby fhigherf quality hydrocarbon products --fboiling vin the tglline and heating oil boiling rangeseare obtained by` aneftcient operation. Infaccprdanceswith the presentinvention,y a residual oil is mildly (thermally 1. cracked; or{. vis broken under .Controlled conditions. Low 4fboilingfhydrocarbon Constituents, ,gas fQr example .hydrocarbons boiling in the motor fuel and heatifrl oil'vboiling ranges are removed from the .-visbrolsenv ..res'i 111.11ml :The vresiduum isl then deasphalted. The resulting :dea spha-lted product `is utilized ,asa h ig h quality fuelVv orvfemployed in the yCatalytic crakinscpsration -Its .wellknown-i ...he ar ,togtreat mineral oils .by various processes in order-,- to .-rernove undesirable hi gh boilinsiand asphalticonstituentsffrsm vrthese.oils Per example, Vit isyknown .to emplev ,light hvdrosarbon; s01- vents'fas y for examples hydrocarbons auch las-fpropanetand butane, in order to remove undesirable constituents,l suehf-,as ea.srh'11ti =..constituentsrthetefrqla slm these 0perations :vafous temperatures.; andv .pressures Yare employed, as well. asyarious srolventjtotoil ratios.. It,r=is-also kiiownin ,the {artf` to yu se various-other; procesjsesfory the removal. of carbon-forming; *andl ashjforming'constituents therefrom j in l order n to prepare high quality tlube `and fueloils. Other ,processes have lso. generallygbeen di,- rected 4 towardv 'thehpreparationsofy Asatisfactory high; boiling feed stocks .-forgaxcrack-ing operatiofparticularly `fora luidized solids catalytic cracking operation.

`It has now been discovered that,undes'irable:high .boilih'sonstiments 7.mw :beeiendv removed-frame feed stocks,boilingY in therI reducedu crude.;v boiling viliugnthe. reduced. crude. or.. `r' sidual.'oil lldly. -vlsbrokfen andjthe'ntreatedlwitha deas'phaltln solvent, as form example, l propane vlor (but'ane. The .process of j the present invention may: be readily understoodfbyrefer-` ence -to the Y'-drravving"illustratingone' embodiment offthe same.

:Referring -ispec-itcall'y tof thedrawingi a ifeed oil,' as for example a--WestTexas crude, .is introduced into distillationrzone 1,1 by. 'means 'of feed line"2. VTemperature and' pressure f .conditionsjgnuzone'` -1 are adjusted .tosccurefthe desired-.fractionation `ofthe-crude goil. .Low boiling hydrocarbongasesare removedvgoverhead from zone 1.by means of fline 3;ahydrocarbonfractionboilingV in Vvthe light naphthaA range .is removed bymeans of line. 51; ahydrocarbon fractionboilingin the heavy naphtlia range3is removedby: means of liners, .while a gsfoillfraction .is'removd byfmails Ofiline 61 frac tion boiling in `the reduced, crude boiling., range, .as for example in u the range above about l6`00" to 700 F., preferably `,boilingvin the range above about 1000 F., v,is segregated vas Aabottoms fraction by-rneansof Vline7. It is to lbe understood -thatzone- 1K may-comprise any suitable) numberI and arrangement' of distillation v`zones or stages.

In accordancey with.^the.present -invention,-the, high boiling --reduced.- crude: .istpassed into: visbreaking zone 10 wherein the `oil fisIv subjected =to temperature;` pressure and time; conditionstomildly reduce the '.viscosityy as hereinafter, described. AI he `,vis rokenjiproducbis.- with drawn from. visbreakingzon'e',

, 2,696,458"y Ice Patented Dec' 7 13.54

and passed into distillation zone 7.1. .Temperature and pressure conditions; in zone 71 are adapted to segregate hydrocarbon'constituents boiling below about '650 F. from theA residuu'm.v Hydrocarbon constituents boil-A ing in the motor` .fuel boilingrange and below. are re- Iiloved from zone'71` by means lof line 72l while hydrocarbon constituents boiling in, .the 'heating oil boiling. range are'removed from zone 71 by meansof line "73sl The Vvisbroken residuum boiling above about 650." F., preferably boiling .above about l000 F. is withdrawn; from..the bottom of distillationzone 71 by means. of line 74 and introduced-finto a' deasphalting 'zone 8 whereinit is preferably countercilrrently contacted witha deasphalting solvent, ,as Afor example, propane. or butano orfequiv'ale'nt v'solvent'.wllich `is introduced :into deasphalting zone 8 Aby means .Online 9. Temperature: and

pressure conditions in zone,V 8 are .adjusted to secure the desiredremov'al of asphalticcon'sttuents' from ythe residual oil. A residuall oil-.propane mixture is `removed overhead fry 'mv zone, 8. by 'means ,of .line'fljant'lV introduced ,into fa' distillation .zone `15'. Temperature andA pressure conditions in Zone 15 are adjusted VAto remove overheadby'-means of.line.50 p1 o'pane or other solvent which is preferably ,recycledto zone `8.

`A*deasphalted-fiesidual fraction is removed from the bottom ofdistillation rzone 15 by means, offline 51 and may be combined kwithaportion fof the gas oil stream withdrawn from zone' 1 lwhich v, i's introduced into. line 51 by meansof line-52." Thisvirgin gas oil `maybe removed fromf the systemif v.desiredby means vofline'tti. The deasp'halted oil may. be, withdrawnfrom. thesystem by means of line, 61` andutilizedjyas a high qualityfuel. The asphaltic constituents 'are 'removed romjzone 8 by.means".of line 5.3 and'passedto a distillation zone 54, wherein a separationis'made ibetween the' propane and Ithe asphaltic constituents.` rTheproparle, or other solvent. is removed vcfsverheadby'means of lineSSfand` preferably recycledl to ,zone 8 while the asphaltic `conprise any suitable number fand.' arrangement `ofy stages.A

' Therpresentinvention is broadly concerned ywithjan improved process forzt'he removal of lundesirable:highV boilinglconstituents and asphaltic constituents rfrommesidual oils. The invention comprises' utilizngin' con-v junction with conventional solvents,'.a, mild" visbreaking operation.' The resultant deasphalted productof'high'er yield, asA pointed lout heretofore, l isA suitable lfor l.the production of high quality fuel'oils, and is'` particularly` adapted as a feedstockl to a fluid catalyticcrackin'g operation.

The deasphalting solvent may comprise low .boiling hydrocarbons,.as for example, thosec'ontaining Yfrom 2 t'o 5 carbon atoms inthe molecule, or mixtures thereof. Particularly desirable solvents comprise propane and butane. -The amount of solvent used per volume of oil may vary from2 to l;l'0',preferably in the range 'from 4 to 6vo1umes of -solvent `per volume of oil. When using propane as a solvent, vthe mixture is generally heatedto a temperature ,in,the,.range from about F. toy 180 F., preferablyl to `a temperature inthe range froml20 to 160 F. When usingbutane asa solvent,` thetemperature maybe inthe rangeof to.350 F., preferably in the range of 200 to 300 F. If a mix- I ture..of;.propane.and blutauelis I`used, intermediate. tempera'tuies to .those used with the ltwomaterials separately are employed.

The deasphalting operation may comprise abatch operation or a countercurrent 'treating' operation wherein the voil is introduced into the ytopfof the`tower,\th`e pr'opane or `other` solvent is'""introduced `into the bottom ofthe tower, and'whereinideasphalted oil is removed;

from the top'of the towerV and asphaltic constituents from the bottom ofthe tower. In conducting" adopgradient is preferably maintained throughout'fthe tower.

As heretoforevdisclosed, the., deasphalted residualk frac tion ,withdrawn from zone.` 15 may be utilized as atuel or -inhaccordance with a, specic adaptation of thepresf enty inventiommaylbe. used as such 4or. combined with-a portion of the gas oil fraction segregated in zone 1 and introduced into a fluid catalytic cracking operation.

The fluid catalytic cracking operation comprises three sections: cracking, regeneration, and fractionation. The cracking reaction takes place continuously in one reactor, the spent catalyst being removed continuously for regeneration in a separate vessel, from which 1t 1s returned to the cracking vessel. Continuity of flow of catalyst as well as of oil is thus accomplished, and the characteristic features of fixed-bed designs involving the intermittent shifting of reactors through cracking, purging, and regeneration cycles are eliminated.

Regenerated catalyst is withdrawn from the regenerator and flows by gravity down a standpipe, wherein a sufficiently high pressure head is built up on the catalyst to allow its injection into the fresh liquid oil stream. The resulting mixture of oil and catalyst ows into the reaction vessel, in which gas velocity is intentionally low, so that a high concentration of catalyst will result. The cracking that takes place results in carbon deposition on the catalyst, requiring regeneration of the catalyst. The cracked product oil vapors are withdrawn from the top of the reactor after passing through cyclone separators to free them of any entrained catalyst particles, while the spent catalyst is withdrawn from the bottom of the reactor and is injected into a stream of undiluted air which carries the catalyst into the regeneration vessel. The products of combustion resulting from the regeneration of the catalyst leave the top of this vessel and pass through a series of cyclones where the bulk of the entrained catalyst is recovered. The regenerated catalyst is withdrawn from the bottom of the vessel to complete its cycle.

Again referring specifically to the drawing, in accordance with a specific preferred adaptation of the present invention, the treated oil removed by means of line 51 is introduced into a catalytic cracking zone 22.

Temperature and pressure conditions in cracking zone 22 are adjusted to secure the desired conversion of the feed oil. Cracked products are removed overhead from zone 22 by means of line 23 and passed into a fractionation zone 24. Temperature and pressure conditions in fractionation zone 24 are adjusted to remove overhead by means of line 25 hydrocarbon constituents boiling in the gasoline and lower boiling ranges. This stream is passed to a stabilizing unit where a gasoline fraction of the desired volatility is segregated. A heating oil fraction is removed by means of line 26 while a fraction boiling in the light cycle oil boiling range is removed by means of line 27. A bottoms fraction or heavy cycle oil is removed by means of line 28 and handled as desired. Spent catalyst is removed from the bottom of zone 22 by means of line 29 and passed into a regeneration zone 30 by means of line 31. Sufcient air is introduced into the system by means of line 32. Regenerated catalyst is removed from the bottom of zone 30 by means of line 33 and passed to the reactor along with the feed by means of line 51.

The invention is broadly concerned with the removal of undesirable materials from petroleum oils, particularly from petroleum oils boiling in the reduced crude boiling range. Petroleum oils treated in accordance with the present invention are particularly adapted as feed stocks for a catalytic cracking reaction. Although the invention may be adapted for the treatment of mineral oils boiling over wide ranges as pointed out above, it is particularly adapted for the treatment of oils boiling above about 860 F., preferably boiling above about 1000 F.

As discussed above, the invention is particularly concerned with an improved operation which comprises the treatment of a reduced crude by visbreaking followed by deasphalting the same. The deasphalted residuum comprises an excellent feed stream for a catalytic cracking unit. It is well known in the art to produce cracked naphthas by a iluidized solids catalytic operation wherein the cracked product comprises constituents boiling in the motor fuel boiling range, as for example, below about 430 F. The cracked product also comprises normally gaseous constituents, as for example, those containing three carbon atoms and less in the molecule. The fluidized solids technique for processing feed fractions, as for example, gas oils, heavy residuums and other feed stocks for the production of hydrocarbon fractions boiling in till) the motor fuel boiling range is a conventional one such as described in conjunction with the drawing.

As pointed out heretofore, the system of a lluidized solids technique comprises a reaction zone and a regeneration zone, employed in conjunction with a fractionation zone. The reactor and the catalyst regenerator are arranged at approximately an even level. The operation of the reaction zone and the regeneration Zone is conventional, which preferably is as follows:

An overflow pan is provided in the regeneration zone at the desired catalyst level. The catalyst overflows into a withdrawal line which preferably has the form of a U- shaped'seal leg connecting the regeneration zone with the reaction zone. The feed stream introduced is usually preheated to a temperature in the range from about 500 to 650 F. in exchangers in heat exchange with regenerator ue gases which are removed overhead from the regeneration zone, or with cracked products. The heated feed stream is withdrawn from the exchangers and introduced into the reactor. The seal leg is usually sufficiently below the point of feed oil injection to prevent oil vapors from backing into the regenerator in case of normal surges. Since there is no restriction in the overflow line from the regenerator, satisfactory catalyst flow will occur as long as the catalyst level in the reactor is slightly below the catalyst level in the regenerator when vessels are carried at about the same pressure. Spent catalyst from the reactor llows through a second U- shaped seal leg from the bottom of the reactor into the bottom of the regenerator. The rate of catalyst flow is controlled by injecting some of the air into catalyst transfer line to the regenerator.

The pressure in the regenerator may be controlled at the desired level by a throttle valve in the overhead line from the regenerator. Thus, the pressure in the regenerator may be controlled at any desired level by a throttle valve which may be operated, if desired, by a differential pressure controller. If the pressure differential between the two vessels is maintained at a minimum, the seal legs will prevent gases from passing from one vessel into the other in the event that the catalyst flow in the legs should cease.

The reactor and the regenerator may be designed for high velocity operation involving linear superficial gas velocities of from about 2.5 to 4 feet per second. However, the superficial velocity of the upowing gases may vary from about 1-5 and higher. Catalyst losses are minimized and substantially prevented in the reactor by the use of multiple stages of cyclone separators. The regeneration zone is provided with cyclone separators. These cyclone separators are usually from 2 to 3 and more stages.

Distributing grids may be employed in the reaction and regeneration zones. Operating temperatures and pressures may vary appreciably depending upon the feed stocks being processed and upon the products desired. Operating temperatures are, for example, in the range from about 800 to 1000 F., preferably about 850-950 F., in the reaction zone. Elevated pressures may be employed, but in general pressures below 100 lbs. per sq. in.

gauge are utilized. Pressures generally in the range from l to 30 lbs. per sq. in. gauge are preferred. A catalyst holdup corresponding to a space velocity of 0.5 to 2O weights per hour of feed per weight of catalyst is utilized. A preferred ratio is l to 3. Catalyst to oil ratios of about 3 to 10, preferably about 6 to 8 by weight are used.

The catalytic materials used in the fluidized catalyst cracking operation, in accordance with the present invention, are conventional cracking catalysts. These catalysts are oxides of metals of groups II, III, IV and V of the periodic table. A preferred catalyst comprises silicaalumina wherein the weight per cent of the alumina is in the range from about 5 to 20%. Another preferred catalyst comprises silica-magnesia where the weight per cent of the magnesia is about 5% to 20%. These catalysts may also contain a third constituent, as for example, ThOz, W03, BeO, BizOs, CdO, U03, B203, Sn02, MnO, CrzOa, CaO, T1203, and CezOs present in the concentration from 0.05% to 0.5%. The size of the catalyst particles is usually below about 200 microns. Usually at least 50% of the catalyst has a micron size in the range from about 20-80. Under these conditions with the superficial velocitiesas given, a uidized bed is maintained ywherein the *lower section of the reactor,- fa" densey catalyst phase exists 'while in the upper area of the reactor -a dispersed phase exists.

The above described operation, as pointed `out, hasno't been entirely satisfactory for cracking heavy oils suchI as a reduced crude due to excessive formation of carbon and ash on the catalyst. However, by mildlyl visbreaking reduced crude and deasphalting the same, unexpected de'- sirable results are secured. y

While the exact mechanism is not entirely understood, it is felt that the mildl visbreaking operation employed as described in the present inventionl causes certain ash constituents in the residuums to decompose. These or# ganic metallic ash compounds are converted 'to -a form which cank readilybe removed on deasphalting.k Itis also felt that these residua4 contain constituents such a's resins which function `as' peptizing agents which tend to hold the oil and asphaltic constituents in a single phase'.y The mild visbreaking` operation of the `pu'esen-tinvention causes these resins to decompose, resulting in a greater yield of deasphalted Loil.

On the other hand, a normal orsevere visbreakingop, eration decreases the yields of deasphalted oil aswell a's impairs, its quality, compared tovmildvisbrealcirr'g;

The mild visbreaking operation is secured by controlling various interrelatedv operatingv conditions such as feed rates, pressure, recycle rates, temperature and time; VIn general it is preferred that relatively low temperatures and contact times be used as compared to normalv visbreaking operations. In visbreaking operations it has been known that the insoluble material in 86 naphtha readily approaches the original Conradson carbon of the feed and then levels oif. One method is to control operating conditions so that a minimum conversion is attained and that the naphtha-insoluble content of the visbroken product (portion boiling above about 650 F.) approaches the Conradson carbon content of the original residuum feed. The viscosity of the product as compared to the feed should be within 50%, preferably within 25%.

The present invention may be more fully understood by the following examples illustrating the same:

EXAMPLE 1 A residual oil was visbroken in one operation to yield 5% by volume of hydrocarbons boiling within the range of butane to about 430 F. vapor temperature. In a second operation, the yield was 9%. Both visbroken products were distilled to remove gasoline and heating oil produced and the higher boiling bottoms fraction was then deasphalted. The results of these operations are shown in the following table. The residua boiled above about 650 F.

visbreaking commons. e Y [nce-throig'h coilV oi:lly.]`Y e G41430F. V.T. Yield, Vol. Percent 5 9 Coil Outlet Temperature, cF 860 920 Coil .Outlet Pressure, p. s. i.` g 350 350 Feed Rate, Vol. of Oil per Hr. per V01. Reactor Zone K above l750"y -j 15.10 1555 Visbroken Tar Yield, Vol. Percent 95 90 4The yieldsof deasphalted oil based upon they virgin residuum in the .two operations were as follows:

Vis'brealr'ing to- Residuum Pretreatment 517 C 97 C Y v ononver- None version lversion 0n Virgin Residuum:

Weight Percent 53 65 6l Volume Percent 55 68 64 .It is readily apparent that the yield of deasphalted 011 is appreciably greater at a 5% conversion as compared to a 9% conversion visbreaking operation.

EXAMPLE 2 Various tests were made to determine the potential carbon which the deasphalted oils would deposit on the catalyst in a uid catalytic cracking operation under the same operating conditions. The results of these tests are as follows:

Catalytic Carbon, Deasphalted Oil From- Wt. Percent on Feed 5% Conversion on Residuum 2. 7 9% Conversion on Residuum 4. 7

Deasphalting of virgin residuum and visbroken resduums [One-stage, using mixed butanes: n-butane and 35% isobutaneJ Material Deasphalted Virgin Residuum Visbreaker Residuum Visbreaker Residuum from 9% Conv. (Ci/430 rela) Deasphalting Conditions:

Temperature SOlvent Trcat Mixing Time.. Settling Time Yiell, Wt. Percent:

Asphalt (72 Vol. Percent) (71 Vol. Percent).

Feed Oil Asphalt Inspections:

Specific Gravity API Gravity Viscosity- SSF/210 F SSF/ F..

SSF/122 F Conradson Carbon, Wt. Percent Insol. 86 Naph. (Mod), Wt. Percent.. Insol. Benzene, Wt. Percent Insol. Carbon Disulde, Wt. Percent. Ash, Wt. Percent Carbon, Wt. Percent.. Hydrogen, Wt. Percen Sulfur, Wt. Percent. H/C Ratio, .Atomic t is apparent fromf the above that approximately 100% more carbon is formed on the catalyst when visbreaking to a 9% conversion as compareduto visbreaking mildly to a 5% conversion.

As pointed out heretofore, the mild visbreaking will be a function of pressure, contact time and temperature. The operations should be so controlled that a minimum conversion is attained wherein the naphtha insoluble content of a visbroken product approaches the Conradson carbon content on the original residuum feed. Effective contact time may be expressed as a reciprocal relationship, v./hr./v., which is volume of feed oil per hour per volume of reaction zone above 750 F. If the ternperature be relatively low, then the contact time is long or the v./hr./v. is relatively low, whereas if higher temperatures are employed, the v./hr./v. is higher. The following table illustrates approximate temperaturev./hr./v. relationships:

What is claimed is:

l. A process for the removal of asphaltic constituents from residual oils which comprises heating the residual oil at a temperature of about 750 F. to 920 F. at a CEI feed rate of aboutl 1-75 volumes of oil per hour per volume of the heating zone to provide a treated product characterized by conversion of no more than about 5% of hydrocarbons boiling in the range below 430 F., removing the said hydrocarbons boiling below about 430 F. by fractionation, and thereafter treating the residual oil` with a deasphalting solvent under conditions to separate asphaltic constituents from the treated product providing a treated residual oil characterized by a viscosity not substantially lower than the original residual oil, and a content of insoluble material in 85 A. P. I. gravity naphtha approaching the Conradson carbon content of the original residual oil.

2. The process dened by claim l in which the said residual oil to be treated boils above about 650 F.

3. The process dened by claim 1 in which the said delasphalting solvent comprises a low boiling hydrocarbon so vent.

References Cited in the tile of this patent UNITED STATES PATENTS Number Name Date 2,160,814 Arveson lune 6, 1939 2,528,586 Ford Nov. 7, 1950 OTHER REFERENCES Industrial and Engineering Chemistry, vol. 42, No. 10, October 1950, pages 2088-2095 incl. (Article by Oden et al.) 

1. A PROCESS FOR THE REMOVAL OF ASPHALTIC CONSTITUENTS FROM RESIDUAL OILS WHICH COMPRISES HEATING THE RESIDUAL OIL AT A TEMPERATURE OF ABOUT 750* F. TO 920* F. AT A FEED RATE OF ABOUT 1-75 VOLUMES OF OIL PER HOUR PER VOLUME OF THE HEATING ZONE TO PROVIDE A TREATED PRODUCT CHARACTERIZED BY CONVERSION OF NO MORE THAN ABOUT 5% OF HYDROCARBONS BOILING IN THE RANGE BELOW 430* F., REMOVING THE SAID HYDROCARBONS BOILING BELOW ABOUT 430* F. BY FRACTIONATION, AND THEREAFTER TREATING THE RESIDUAL OIL WITH A DEASPHALTING SOLVENT UNDER CONDITIONS TO SEPARATE ASPHALTIC CONSTITUENTS FROM THE TREATED PRODUCT PROVIDING A TREATED RESIDUAL OIL CHARACTERIZED BY A VISCOSITY NOT SUBSTANTIALLY LOWER THAN THE ORIGINAL RESIDUAL OIL, AND A CONTENT OF INSOLUBLE MATERIAL IN 85* A. P. I. GRAVITY NAPHTHA APPROACHING THE CONRADSON CARBON CONTENT OF THE ORIGINAL RESIDUAL OIL. 